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October 4, 2008 - 9:32pm
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Every room has a optimum listening volume?
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With nothing but my own experience, I'd say that Yes, each room has a sound pressure limit at which the music begins to mush together after. Of course it also is dependant on how reflective or absorptive, it's shape and all the normal factors in room acoustics.
And let's not forget that often you reach that "limit" based on the system itself; speaker efficiency and amplifier power, etc. On this point DUP is at least somewhat correct (it's just he overstates it's importance above everything else). Power, watts and amplifier reserves certainly do matter, as does speaker size and frequency range. Crank up a cheap system, or even a modest one that is just not full range, and it falls apart long before the room reaches it's acoustic limit.
My 2 cents.
I'll lean in and agree with Doug.
I think it is actually a very important part of the equation.
Thanks guys for your responses. It justifies the need for room treatment i.e if you really want the room to behave.
Sort of.
Rooms and room acoustics are linear, so whatever happens at low levels happens the same at high levels. Other than buzzing windows etc that might occur only at very loud levels. The key is your friend's comment about how loud or soft we can hear things clearly.
If a room is untreated and has too much ambience, that ambience will be audible at fairly low levels. Lets say the sum of all reflections is only 20 dB below the music. In that case the reflections are a nuisance at relatively low SPL levels. If the room is treated so the sum of all reflections is 40 dB below the music, then you can play the music that much louder before the reflections are audible and thus intrusive.
--Ethan
Ethan, I am certain you are correct that the effects are linear.
However, as a performer I know that one can overload a given room while playing. It isn't just that it gets "too load" and becomes uncomfortable. Something seems to happen where the sound falls apart.
It's as if at a certain loudness the room starts to fight back and the quality of the sound changes.
Thoughts?
Yes, and that point is where the reflections are audible enough to be noticed. We all know that you can hear detail more clearly when the volume is raised. Likewise for the "detail" of intrusive reflections. I can't imagine another explanation that makes more sense.
--Ethan
A cool thing about a well treated room is that the treatments make the room "larger" with regard to this issue!
Yes, both absorption and diffusion do that. When the reflections are absorbed it's as if the room boundaries are infinitely far away. Or at least farther away. Diffusion has a similar effect, and can make a small room sound much larger.
--Ethan
I think that as the loudness goes up the flexing of the walls (really) starts adding more timing issues and things break apart.
Elk, have you ever made the room "ring". I've got a relatively small studio, with a carpeted floor, but relatively large window space. The glass starts to ring (not rattle) if I play high and loud enough. These are large panes, about 3-feet square. It'll keep up for a part of a second when I stop playing.
Also, it's interesting to note that as I move around the room and point my bell in different directions, the capacity to accept volume can vary dramatically. I think it is mostly reflection related, but it's also flex related.
Dave
Dave, all of those things - glass ringing, walls flexing - should be linear over a wide range of SPL levels. If you have software to measure your room this is very easy to determine. Simply measure at a relatively low level, then again 20 dB louder. If the waterfall charts have the same basic decay times, that shows the ringing is present at lower levels too but you just don't hear it as clearly.
--Ethan
Not only can glass ring, one can get sort of a ringing sound from slap echo. Weird stuff.
Ethan, you're probably right with the explanation. Yet the experience makes it feel more exponential than linear. It's as if there is a tipping point where suddenly the room goes wild and there is almost a feedback sort of effect. This happens in both small and large rooms.
Another thing that I think many audio listeners do is to turn up the volume until they hear the room. That is, it just doesn't seem to be an active "room filling" system until it reaches a certain loudness and the room is loaded.
We certainly do this as musicians. It is one of the things that makes playing outside so difficult. Without any walls the space doesn't talk back. As a result most of us tend to play too loud.
If the walls and surfaces didn't flex, then I'd likely agree that everything is linear; however, I think that, particularly at higher frequencies, the flex of the surfaces will disrupt the timing enough to distort the sound. The surface will be giving off it's own sound which must mix with new reflected sound. It'll often be out of phase because the signals are not in sync.
With long wave lengths at lower frequencies the timing differences will be inconsequential, but I think that it become very nasty at higher frequencies.
Using a very focus projector, like a trumpet, it's easy to hear these disturbances in isolation. When you get full range music going with two cabinets and several drivers and the flexing aggravated further by the power of the bass, then the upper frequency smear will be there, but harder to separate. All you'll hear is uglyness and harshness. (Without fail, it gets harsh and it's NOT due to the tone of the instrument).
Dave
It may not sound linear, but it has to be. However, ears are exponential. I'll mention that my living room does not have this effect. Music sounds the same at all volume levels, other than the normal changes due to Fletcher-Munson. I can play stuff very loudly and never hear the room. The sound never "blossoms" if you will.
--Ethan
Wall flexing is linear too. At extreme SPL levels the surfaces may bottom out, but that'd have to much louder than anyone could tolerate. Also, walls mostly do not flex except at the very lowest frequencies. I can't imagine any note a trumpet can play would be able to move 5/8 inch sheet rock very much. This too is easy to test. Play loud bassy music and put your hand against the wall (or glass window). I'm sure you can feel the vibration. Now do the same at 500 Hz.
That doesn't make sense to me. I can't see how a wall surface could generate sound on its own. And if it did, there'd be no phase relation to the original music or the reflected music.
If I misunderstood your point, please clarify.
--Ethan
If the wall is moving, then it'll be giving off a sound. It's easier to hear at higher frequencies, such as my example of the window glass ringing when I play a high, loud note with my trumpet.
The wave lengths are so long in bass notes that this is not an issue, I suspect; however, the high frequency ringing will be out of phase with the sound from the speakers, probably causing intermodulation disortion that we identify as a harshness in the sound. I think that as volume goes up, there's a "tipping point" the room overloads.
I think what makes it non-linear is that the vibration will grow in amplitude as the loudness increases, particularly the bass frequencies. Then the arrival/reflection times will vary more as the walls move further in and out. The measure effect in bass frequencies will be next to nothing, but at higher frequencies I think there'll be a point of breakup that's nonlinear.
I may be wrong, but that's what I think that I hear. Also, consider the resonant frequencies of the various reflective surfaces. The build up of those resonances will be linear I suspect, but when you change the stimulating note and the surface continues to vibrate at its resonant frequency, a disonant note will react out of phase potentially, leading to nonlinear response.
Still, I think we're really address room resonance, reflected sounds and the interaction of those, leading to intermodulation disortion.
Dave
Yes, but that is sympathetic vibration, which means it's merely repeating a stimulus.
That's still a linear system.
Yes, that can definitely happen, and it shows up clearly in a waterfall plot. The audible effect is usually more of reverb than IM distortion, because it's a continuation of sound that was already present in the room.
--Ethan
My experience is like Dave's; overloading the room is always harsh.
It also does not depend on the size of the room. Performances meant for chamber music can have this effect if filled with a brass band or other louder group.
Dave, are you sure that it is the glass that rings? I have never given this specific thought other than to assume that there was reflected sound that was in turn reflecting off of another hard surface, until it died out.
I assume that a large stone church would similarly ring, but we don't hear it because of the much louder reverb.
I agree with Ethan that a well treated room or acoustically designed space does not have any of these effects, at least not that I have experienced.
Large spaces don't ring as much have reverb. Another factor that could make ringing in a smaller room sound like IMD is that ringing can be excited by a frequency near, but not quite at, a frequency sounding in the room. So if the room rings at 450 Hz and you play a loud A note, that could sound out of tune or possibly even dissonant.
--Ethan
The effect may be linear (it's math so it has to be) but our hearing isn't linear so that may explain why as volume raises the negative effects of acoustics seem to become subjectively worse. That's also what my anecdotal experience supports.
No Elk, I'm not certain that it's the glass, but it does seem to amplify when I aim at the glass. I can also hear something similar when I aim the bell into the corner of the room. It's not a chime-like sound, but it's like an electronic signal or a very high harmonic in isolation. It rings for almost a second.
Dave
I know precisely the sound you describe.
Maybe it is the glass.
Yes, and this is exactly what I've been saying all along.
I have found that if you replace the regular glass with what is known as "safety glass" you can minimize the ringing. This is a worthy change.
Really?
Are you referring to safety glass with a contained layer of plastic film between two sheets of glass?
In my own personal opinion, I would think that there are so many other variables to the equation that "safety glass" is to simple of an answer. The thickness of the glass, the dimensions and area of the glass. The location of the glass in the room relative to the rooms dimensions and its modes.
Just a thought.
My windows will hum at a surprisingly low volume at the right frequency.
Of course, my room is rather small and it's easy to overload. I can really
get them to sing with JA's test discs.
...that
what is "NC"?
...in North Carolina
thought so. I am in NC too, wilmington.
is your group in raleigh?
I just left germany after living there for many years.
Yes, Mike is from Raleigh. If you want you can listen the WFS in the spring, is two hours to drive as far as I know.
Where are you was living in Germany? You were able for listen the WFS Loudspeaker rows which are working in Berlin, Ilmenau or Munich? It